1. Field of the Invention
The present invention is generally related to devices and methods for adjusting gain, and more particularly, to a device and method for automatically adjusting gain.
2. Description of Related Art
There are various commercially available digital video systems or digital media players, such as digital video recorders (DVR), personal video recorders (PVR), MP3 players, voice recorders, and the like, for playing back audio signals. Specific sources of audio signals of digital video systems or digital media players include TV, files, disks, and other types of media. Switching between audio signals originating from different sources and played back by digital media players renders the output audio signals unstable due to discrepancies in audio signal sources and file formats.
One example from common experience is watching TV. A user who sets a TV set to a desirable volume level before watching a movie on the TV set expects a consistent output of audio signals of the movie being played on the TV set. Nonetheless, the user often perceives a sudden amplification of audio signals whenever the movie is interrupted by a television advertisement. This is because the audio signals of the movie are different from those of the television advertisement. As a result, an otherwise effortless movie watching session sees the user alternating between manually turning down the TV set when a TV advertisement appears and manually turning up the TV set when the TV advertisement disappears, causing the user inconvenience.
For this reason, U.S. Pat. No. 7,072,477 proposes a method and apparatus for automatically normalizing a perceived volume level in a digitally encoded file. The method includes the steps of selecting a number of frequency bands to calculate a gain factor for adjusting the output volume level and normalizing the output volume level. However, the method disclosed in U.S. Pat. No. 7,072,477 entails selecting appropriate frequency bands. Users may not know how to select appropriate frequency bands, and predetermined frequency bands may not match input audio signals. As a result the output audio signals do not meet the users' auditory needs, despite adjustment. Accordingly, the drawback of the prior art is an issue that calls for an immediate solution.